Evaluation of the Direct Toxicity of Trioctyltrimellitate (TOTM), di(2-ethylhexyl) Phthalate (DEHP) and their Hydrolysis Products on Isolated Rat Hepatocytes

Abstract

Plasticizers are added to polyvinyl chloride (PVC) to confer flexibility to the polymer. Di-(2-ethylhexyl) phthalate (DEHP) is the most commonly used of them. However, due to its non covalent bond to the PVC, DEHP tends to vaporize easily. A significant exposure has been recorded in dialyzed patients since medical tubings. Most animal species metabolize DEHP rapidly into mono-ethylhexyl phthalate (MEHP) and 2-ethylhexanol (2-EH). Because of the suspected toxicity of DEHP, an alternative plasticizer, trioctyltrimellitate (TOTM) has aroused increasing interest. The aim of this study was to determine on isolated rat hepatocytes in vitro, the direct hepatotoxic potential of both DEHP and TOTM and their hydrolytic products. To evaluate the possible toxic liver risk resulting from exposure to DEHP and TOTM, isolated rat hepatocytes were incubated with either DEHP, TOTM, MEHP or their common metabolite (2-EH) for 3 hours. Cell viability was periodically estimated thanks to trypan blue tests (15 - 180 min). The activity of lactate dehydrogenase (LDH) was also monitored (1h, 2h, 3h). The results obtained with trypan blue test and with direct LDH activity measurements, were satisfactorily correlated. Hepatocytes treated with both plasticizers and metabolites on the one hand, and the controls (untreated suspension) on the other hand, showed important differences as for cell viability. The acute toxicity on hepatocytes is mainly due to MEHP. Among DEHP, TOTM, MEHP, 2-EH and after intraperitoneal injection of those compounds, only DEHP and MEHP were able to induce a significant hydrogen peroxide (H2O2) production by the rat hepatocytes. These observations enable us to confirm the hypothesis according to which DEHP and MEHP cause an imbalance between the synthesis and the degradation of H2O2. Our results suggest a short-term in vitro cytotoxicity of MEHP. Even if trypan blue and LDH tests offered good results and were easily branded, further assays as well as MTT-tests should performed in order to confirm the cytotoxicity of the compounds tested.

Comprehensive review of 2-ethyl-1-hexanol as an indoor air pollutant

“…117 After intraperitoneal injection, 2EH did not induce a significant production of hydrogen peroxide generated by peroxisome proliferators in the rat hepatocytes. 118…”

Effects of Exposure to Plasticizers Di-(2-Ethylhexyl) Phthalate and Trioctyltrimellitate on the Histological Structure of Adult Male Albino Rats’ Liver

“…Tasci et al [21] stated that disorganization of nuclear content as margination and clumping of chromatin in saline treated animals may be morphological evidence of injury in the nucleus. Kambia et al [11] reported that, following TOTM administration, high rate of new mitochondrial membrane formation is due to increased endogenous mitochondrial protein synthesis in addition to increased rate of membrane phospholipid synthesis by about 20%.Sections of the same group showed dilated tubules of sER of hepatocytes. Since sER plays a prominent role in the metabolic transformation of drugs and toxins.…”

“…TOTM have been found to be non-mutagenic. It is not able to bind to peroxisome proliferator-activated receptors (PPARs) [11].…”

Simultaneous determination of polyvinylchloride plasticizers di(2-ethylhexyl) phthalate and tri(2-ethylhexyl) trimellitate and its degradation products in blood by liquid chromatography-tandem mass spectrometry

“…First results indicate that TOTM actually possesses a lower toxicity than DEHP [2,[18][19][20]. Moreover, a higher chemical stability can be assumed indicated by a significantly decreased leachability of TOTM from PVC medical devices into intravenous preparations [21] and into blood [10].…”